How To Block Someone From Sending A Message
If you have politely declined to speak with someone and blocking them is necessary, it can be done quickly and easily with a few steps. First, open the conversation thread of the person you want to block.
Go to "Inbox"
Click on a message
Click on the three dots in the top right hand corner of the messages
Select "Block User"
To unblock a user click the three dots top left hand side (next to your name)
Scroll down to blocked users and select the one you want to unblock